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Effects of Land Use on the Spatial and Vertical Distribution of Arsenic in Soil Cores on Oahu

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Title:Effects of Land Use on the Spatial and Vertical Distribution of Arsenic in Soil Cores on Oahu
Authors:Thomas, Sara
Contributors:De Carlo, Eric (advisor)
Oceanography (department)
Global Environmental Science (department)
Date Issued:2009
Publisher:University of Hawaiʻi at Mānoa
Place of Publication:Honolulu
Abstract:Soil cores were analyzed using Inductively Coupled Plasma Mass Spectrometry
(ICP-MS) to determine the effects of land use on spatial and vertical distribution of
arsenic (As) in soils around the island of O’ahu, Hawai’i. Six cores were collected and
divided into 10 cm increments at five locations. Two cores were obtained from a
gardenia farm (WK1 and WK3) and one in a forested region of Manoa Valley (WK2),
one from the Lyon Arboretum (LA), and two from fallow pineapple and sugarcane fields
in Kunia (KU) and Waipahu (WAI), respectively.
Concentrations of As were above 500 ppm in all three of the cores taken along the
Waikeakua Stream in Manoa. The concentrations are consistent with the hypothesis that
As is introduced to soils through anthropogenic activity, either the application of
superphosphate fertilizers or pesticides. High concentrations in the forested area suggest
prior human activity in Manoa Valley has left soils with elevated concentrations of As.
Relatively low, yet still elevated over natural, concentrations of As measured in the WAI
core suggest alternative methods of pest and weed control were applied to sugarcane
crops in this field. Both the LA and KU core demonstrated concentrations of As similar
to Hawaiian background levels.
In cores with As contamination, concentrations decrease as a function of depth
but maximum concentrations in the soil column occur at 10-20 cm depth. Drastic
decreases in concentrations of As below this depth may be due to the strong affinity of As
to iron oxides (FeOx) in soils at the surface where As is introduced through anthropogenic
activity. Tilling of surface soils or the uptake of As from surface soils by plants may
account for the observed subsurface peak in concentration of As.
Pages/Duration:65 pages
Rights:All UHM dissertations and theses are protected by copyright. They may be viewed from this source for any purpose, but reproduction or distribution in any format is prohibited without written permission from the copyright owner.
Rights Holder:Thomas, Sara
Appears in Collections: Global Environmental Science Theses

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